In an air conditioner which performs indoor space cooling, the evaporative temperature of a utilization-side heat exchanger may fall during a cooling operation in some cases. If the cooling operation is continued in such a state, this causes drain water adhering to the surface of the utilization-side heat exchanger to freeze to ice. The adhesion of ice to the surface of the utilization-side heat exchanger inhibits heat exchange between refrigerant and air in the utilization-side heat exchanger. To cope with this problem, air conditioners which perform such a cooling operation are so configured as to execute an ice melting operation for melting adhered ice. In the ice melting operation, the expansion valve is closed to stop inflow of refrigerant and air is fed to the utilization-side heat exchanger to thereby melt ice adhering thereto. This type of air conditioner is disclosed, for example, in JP-A-H03-186135 and JP-A-H10-26429.
More specifically, referring to FIG. 2 of JP-A-H03-186135, there is shown an air conditioner in which three indoor units are provided with respect to a single outdoor unit. Each indoor unit has a respective liquid temperature sensor for measuring the temperature of liquid refrigerant in an associated indoor-side heat exchanger. The air conditioner includes a control unit. The control unit is so configured as to terminate the ice melting operation upon elapse of a reference time since the value of measurement taken by the liquid temperature sensor exceeded a reference temperature.
In addition, referring to FIG. 1 of JP-A-H10-26429, there is shown an air conditioner in which two indoor units are provided with respect to a single outdoor unit. In an indoor-side heat exchanger of each indoor unit, a heat exchange temperature sensor is provided as a means for detecting whether there is leakage of refrigerant from an expansion valve. In the air conditioner, it is configured such that, in the event of detection of refrigerant leakage during the ice melting operation, a recovery operation is carried out whereby the expansion valve is repeatedly alternately fully opened/closed in order to eliminate the refrigerant leakage.